December 3, 2020
Generally speaking, the shelf life of the drying grade of ferrous sulfate heptahydrate is generally about one year, and the shelf life of ferrous sulfate monohydrate is dried in a high-temperature brick kiln, and the shelf life is not more than two years. If ferrous sulfate is stored for too long, it will deteriorate. How does the deterioration of ferrous sulfate occur?
The deterioration of ferrous sulfate is because it has strong reducing properties. After being placed in the air for a long time, it will react with the air, hydrolyze in the air, and slowly oxidize to ferrous sulfate or oxidized ferrous sulfate. Ionic ferrous iron will be slowly oxidized to ferric iron (Fe+3), and ferrous sulfate heptahydrate will turn from the initial light green to yellowish-brown. After the product is oxidized to ferric iron, it will be dissolved in the preparation solution, there will be sediment and suspended matter, and the solution will also be yellow. After the solid ferrous iron deteriorates, it will form yellow lumps, and the chemical properties will change after deterioration, and the effect will be greatly reduced.
Methods to prevent deterioration of ferrous iron:
Add iron powder (iron element) to ferrous sulfate or the solution, because ferrous sulfate is oxidized to produce ferric sulfate, but the reaction of ferric sulfate with iron can produce ferrous sulfate Fe+2Fe3+=3Fe2+. For solid products, it is recommended to prepare them for immediate use and not to store them for a long time after being dissolved in water.